Nuclear Mishap Stuns Regulators

June 23, 1985|By Casey Bukro, Environment writer.

TOLEDO — Just when memories of Three Mile Island appeared to be fading, the American nuclear enterprise was shaken again this month by a series of malfunctions and human error at the Davis-Besse power station. It was an unnerving replay of the early minutes of the infamous 1979 partial meltdown in Pennsylvania.

The Davis-Besse mishap lasted 16 minutes on June 9 before the $943 million plant shut down safely. There were no injuries, radioactive releases or reactor damage.

Yet the Nuclear Regulatory Commission considers the event serious because it raises disturbing questions about the ability of Toledo Edison Co. to operate the Davis-Besse plant, and of the NRC itself to manage nuclear power plants safely.

So serious, in fact, that reaction was uncommonly swift, and even unique. -- The NRC, for the first time, dispatched a ``SWAT team`` of nuclear safety experts to Davis-Besse. The investigation is patterned on aviation safety inquiries at the scenes of aircraft crashes.

-- Toledo Edison announced two major management changes last week, naming a new president, Paul Smart, and new chief of the utility`s nuclear division, retired Navy Adm. Joe Williams.

-- The House Subcommittee on Energy Conservation and Power asked top NRC officials to appear at a briefing Friday on ``management deficiencies at Davis-Besse`` and on NRC responsibility for allowing the plant to operate despite concerns over plant safety dating to 1980.

``It`s viewed as serious because, had feedwater not been restored, it is questionable whether the plant could have survived without fuel damage,`` said James Keppler, the NRC`s Midwest regional chief.

Keppler described Friday`s session as ``a tough meeting`` in which both the NRC and Toledo Edison were criticized for failing to install an extra feedwater pump at Davis-Besse in the last five years, though a 1980 NRC memo called the safety improvement ``of highest priority.`` More hearings were being scheduled.

The Three Mile Island nuclear plant near Harrisburg, Pa., suffered a partial fuel meltdown in 1979 because a series of mechanical and operator errors robbed the plant of cooling water for almost three hours.

Ten NRC officials are at Davis-Besse, including four from Washington who are acting as an independent investigative task force. Top NRC officials want a report in 30 days, and several say the nuclear plant could be shut for the rest of the year.

``The second reason for the intense effort is that it has been recommended that we have something similar to a national accident review board, like they have in the airline industry,`` Keppler said. ``This is the first attempt to try this proposal.``

The Davis-Besse mishaps began at 1:35 a.m. June 9 when two main feedwater pumps supplying water to the nuclear plant shut down unexpectedly. The nuclear reactor automatically shut down 27 seconds later, but the hot reactor system still needed fresh supplies of water to keep temperatures from rising dangerously.

Two back-up water pumps started, but they immediately turned off. At this point, four major water pumps had failed, including two that were intended for use in emergencies.

Loss of this water supply caused pressure and temperatures in the reactor system to rise. As a result, a pressure relief valve popped open and stuck in the open position.

A reactor operator in the control room pushed two wrong buttons, closing valves that should have been open, but corrected the error.

By 1:51 a.m., the Davis-Besse staff got a feedwater pump going and closed the stuck valve, ending the mishap.

The NRC counted 12 mechanical failures, many of them unexplained, and one human error.

The NRC was stunned by the sequence of malfunctions.

``What makes it so unsettling is the auxiliary (back-up) feed pumps went out and the relief valve stayed open,`` said Russell Marabito, an NRC spokesman. ``It was like the early stages of TMI, although you never got to the final stages.``

Davis-Besse has a reputation as an omen of the Three Mile Island accident. In 1977, a similar sequence of mechanical failures, again involving feedwater pumps and the same relief valve, struck Davis-Besse for 20 minutes before the plant was shut down safely.

Then the same series of failures struck at Three Mile Island in 1979, with catastrophic results. Three Mile Island operators in 1980 sued the NRC for $4 billion in damages, claiming the agency was negligent in failing to alert Three Mile Island about the valve problem in the 1977 Davis-Besse accident. The U.S. Supreme Court dismissed the suit last February.

The NRC still is smarting from that, and it could be left smarting from the newest Davis-Besse incident.

Keppler noted that Davis-Besse is known to have a ``marginally acceptable core cooling system.`` Five years ago, the NRC gave Toledo Edison until 1986 to install an additional feedwater pump and allowed the plant to keep operating.

The Davis-Besse reactor has tripped off automatically five times this year, which is another reason for NRC concern. Trips are sudden, automatic shutdowns of nuclear reactors, similar to jamming the brakes of an automobile traveling 65 miles an hour. Such emergency stops put stress on reactor systems and should be avoided.

When the Davis-Besse reactor trips off, 1,000 pounds per square inch of pressure comes roaring out of a safety valve, and residents of farms nearby know the sound.

Edythe Hemminger, who lives on a 65-acre farm across a highway from Davis-Besse, said:

``It really startles you when it goes off. It sounds like a jet coming at you. It really sits you up in bed. But you get used to it. We have a lot of friends who work there (at Davis-Besse) and they say not to worry. We take their word.``